Thermoplastic olefin elastomer composition

ABSTRACT

An olefin-based thermoplastic elastomer composition comprising a thermoplastic elastomer blended with other resins and rubbers is provided. The thermoplastic elastomer contains polypropylene resin and an olefin-based copolymer rubber, and optionally, a linear polyethylene resin, and the thermoplastic elastomer has been crosslinked to a gel content of 95% or higher. A polyolefin resin, an olefin-based copolymer rubber and a softening agent are further blended with optional inorganic filler to provide the olefin-based thermoplastic elastomer composition. This composition is excellent in oil resistance and extrudability, and well-adapted for use as an energy-saving, resources-saving elastomer in applications including surface or skin material in autoparts, industrial mechanical parts, electric and electronic parts, and construction materials.

This application is the national phase under 35 U.S.C. § 371 of PCTInternational Application No. PCT/JP98/03811 which has an Internationalfiling date of Aug. 27, 1998, which designated the United States ofAmerica.

FIELD OF THE INVENTION

This invention relates to an olefin-based thermoplastic elastomercomposition, and more specifically, to an olefin-based thermoplasticelastomer composition having excellent oil resistance.

BACKGROUND ART

Olefin-based thermoplastic elastomers are excellent in moldability,flexibility and heat resistance, and their industrial use has expandedin various fields because of such favorable properties. Olefin-basedthermoplastic elastomers are also light-weighted and easy to recycle,and such features also backed their use as energy-saving,resources-saving elastomeric substitutes for vulcanized rubbers in thefield of auto-parts, industrial mechanical parts, electric andelectronic parts, construction materials, and the like.

Olefin-based thermoplastic elastomers, however, suffered from theproblem of insufficient oil resistance, and when they are brought incontact with a non-polar solvent such as an aromatic organic solvent,gasoline and mineral oil, they undergo swelling. Such drawback resultedin their limited use.

In view of the situation as described above, an object of the presentinvention is to solve the problems associated with the prior art, and toprovide an olefin-based thermoplastic elastomer composition which hasexcellent oil resistance as well as excellent moldability.

DISCLOSURE OF THE INVENTION

According to the present-invention, there is provided an olefin-basedthermoplastic elastomer composition comprising

(I) 100 parts by weight of an elastomer containing

(A) 20 to 90 parts by weight of a polypropylene resin having a melt flowrate 0.1 to 5 g/10 min when the melt flow rate is measured under theload of 2.16 kg and the temperature of 230° C. in accordance with ASTMD1238, and

(C) 10 to 80 parts by weight of an olefin-based copolymer rubber((A)+(C)=100 parts by weight), and which has been crosslinked to a gelcontent of at least 95%;

(D) 10 to 300 parts by weight of a polyolefin-based resin;

(E) 10 to 300 parts by weight of an olefin-based copolymer rubber; and

(F) 10 to 300 parts by weight of a softening agent; wherein weightdifference (ΔW) of said composition before and after immersing in liquidparaffin at 100° C. for 24 hours is up to 150%.

According to the present invention, there is also provided anolefin-based thermoplastic elastomer composition comprising

(I) 100 parts by weight of an elastomer containing

(A) 20 to 90 parts by weight of a polypropylene resin having a melt flowrate 0.1 to 5 g/10 min when the melt flow rate is measured under theload of 2.16 kg and the temperature of 230° C. in accordance with ASTMD1238,

(B) 5 to 30 parts by weight of a linear polyethylene resin having adensity of 0.920 to 0.950 g/cm³, and

(C) 5 to 75 parts by weight of an olefin-based copolymer rubber((A)+(B)+(C)=100 parts by weight), and

which has been crosslinked to a gel content of at least 95%;

(D) 10 to 300 parts by weight of a polyolefin-based resin;

(E) 10 to 300 parts by weight of an olefin-based copolymer rubber; and

(F) 10 to 300 parts by weight of a softening agent; wherein weightdifference (ΔW) of said composition before and after immersing in liquidparaffin at 100° C. for 24 hours is up to 150%.

According to a preferred embodiment of the present invention, there isalso provided an olefin-based thermoplastic elastomer compositionwherein the composition contains the components (A) and (C), or thecomponents (A), (B) and (C) as the elastomer (I) which has been producedby crosslinking said components by dynamic heat treatment in thepresence of an organic peroxide.

Next, the olefin-based thermoplastic elastomer composition of thepresent invention (hereinafter referred to as the present composition)is described in detail.

The polypropylene resin (A) which is the a critical component of thepresent composition is a polymer containing propylene as its maincomponent, and exemplary such polypropylene resin (A) include:

(1) propylene homopolymer,

(2) a random copolymer of propylene with up to 10% by mole of anα-olefin other than propylene, and

(3) a block copolymer of propylene with up to 30% by mole of an α-olefinother than propylene.

Exemplary such α-olefins other than propylene include ethylene,1-butene, 4-methyl-1-pentene, 1-hexene, and 1-octene, and the polymermay include such α-olefin either alone or in combination of two or more.The polypropylene resin (A) may include the polymers as described aboveeither alone or in combination of two or more. Of the polymers asdescribed above, the preferred is the propylene homopolymer.

In view of the improved oil resistance and sufficient moldability of theresulting olefin-based thermoplastic elastomer composition, thepolypropylene resin (A) is preferably the one having a melt flow rate of0.1 to 5 g/10 min, and more preferably 0.5 to 3 g/10 min when the meltflow rate is measured under the load of 2.16 kg and at a temperature of230° C. in accordance with ASTM D1238.

The linear polyethylene resin (B) used as a constituent of the presentcomposition is typically a random copolymer of ethylene with an(α-olefin containing 3 to 10 carbon atoms. Use of a linear polyethyleneresin results in the improved compatibility between the propylene resin(A) and the olefin-based copolymer rubber (C), and in particular, in theimproved extrudability of the resulting composition. Exemplary α-olefinscontaining 3 to 10 carbon atoms include propyelene, 1-butene,4-methyl-1-pentene, 1-hexene, and 1-octene, and the preferred amongthese are 4-methyl-1-pentene and 1-hexene. The random copolymer of theethylene with such α-olefin may contain either one or two or more ofsuch an α-olefin. The linear polyethylene resin is preferably anethylene/4-methyl-1-pentene random copolymer.

The α-olefin is copolymerized in the polyethylene resin (B) preferablyin an amount of 1 to 8% by mole, and more preferably, in an amount of 2to 5% by mole.

The polyethylene resin (B) has a density of 0.920 to 0.950 g/cm³, andpreferably, a density of 0.925 to 0.945 g/cm³. When the density is lessthan 0.920 g/cm³, the resulting olefin-based thermoplastic elastomercomposition suffers from insufficient oil resistance and the object ofthe present invention will not be attained. Therefore, the limitation ofthe density is important.

In addition, the polyethylene resin (B) may preferably have a melt flowrate (MFR) of 0.1 to 50 g/10 min, and most preferably, a melt flow rateof 1 to 30 g/10 min when evaluated in accordance with ASTM D1238 underthe load of 2.16 kg and at a temperature of 190° C. The melt flow ratein excess of 50 g/10 min results in the insufficient oil resistancewhile the melt flow rate of less than 0.1 g/10 min results in theinsufficient moldability.

The olefin-based copolymer rubber (C) which is a critical component ofthe present invention may be a copolymer rubber containing an α-olefinas its main component. This copolymer rubber is an amorphous, random,elastic copolymer such as an α-olefin copolymer comprising two or moreα-olefins containing 2 to 20 carbon atoms, and an α-olefin/nonconjugateddiene copolymer comprising two or more α-olefins containing 2 to 20carbon atoms and a nonconjugated diene.

Exemplary olefin-based copolymer rubbers include:

(1) Copolymer rubber of ethylene and an α-olefin other than ethylene

[Ethylene/α-olefin other than ethylene (molar ratio)=90/10 to 50/50]

(2) Copolymer rubber of ethylene, an α-olefin other than ethylene, and anonconjugated diene

[Ethylene/α-olefin other than ethylene (molar ratio)=90/10 to 50/50]

[Ethylene/nonconjugated diene (molar ratio)=99/1 to 90/10]

(3) Copolymer rubber of propylene and an α-olefin other than propylene

[Propylene/α-olefin other than propylene (molar ratio)=90/10 to 50/50]

(4) Copolymer rubber of butene and an α-olefin other than butene

[Butene/α-olefin other than butene (molar ratio)=90/10 to 50/50]

Exemplary α-olefins include ethylene, propylene, 1-butene,4-methyl-1-pentene, 1-hexene, 1-octene, and the like.

Exemplary nonconjugated dienes include dicyclopentadiene, 1,4-hexadiene,cyclooctadiene, methylene norbornene, ethylidene norbornene, and thelike.

The copolymer rubbers (1) to (4) as described above may preferably havea Mooney viscosity [ML₁₊₄ (100° C.)] of 10 to 250, and most preferably,30 to 150. The copolymer rubber (2) of ethylene, α-olefin other thanethylene and a nonconjugated diene may preferably have an iodine valueof up to 25.

In the present invention, the content of the polypropylene resin (A) inthe elastomer (I) is 20 to 90 parts by weight, and preferably 20 to 60parts by weight based on 100 parts by weight of total ((A)+(C)) of thepolypropylene resin (A) and the olefin-based copolymer rubber (C) or 100parts by weight of total ((A)+(B)+(C)) of the polypropylene resin (A),the linear polyethylene resin (B), and the olefin-based copolymer rubber(C).

When the polypropylene resin (A) is used in such amount, the resultingolefin-based thermoplastic elastomer composition will exhibit excellentresistance to oil and heat as well as good extrudability.

In the present invention, content of the polyethylene resin (B) in theelastomer (I) is 5 to 30 parts by weight, and preferably 5 to 20 partsby weight based on 100 parts by weight of total ((A)+(B)+(C)) of thepolypropylene resin (A) and the linear polyethylene resin (B) asdescribed above and the olefin-based copolymer rubber (C) as describedbelow. When the polyethylene resin (B) is used in such amount, theresulting olefin-based thermoplastic elastomer composition will exhibitexcellent resistance to oil and heat as well as good extrudability.

In the present invention, content of the olefin-based copolymer rubber(C) in the elastomer (I) is 5 to 75 parts by weight, and preferably 20to 75 parts by weight based on 100 parts by weight of total((A)+(B)+(C)) of the polypropylene resin (A), the linear polyethyleneresin (B) and the olefin-based copolymer rubber (C). Content of theolefin-based copolymer rubber (C) free from the polyethylene resin (B)is 10 to 80 parts by weight, and preferably 20 to 75 parts by weightbased on 100 parts by weight of total ((A)+(C)) of the polypropyleneresin (A) and the olefin-based copolymer rubber (C).

When the olefin-based copolymer rubber (C) is used in such amount, theresulting olefin-based thermoplastic elastomer composition will exhibitexcellent oil resistance as well as sufficient flexibility.

In the present invention, the olefin-based copolymer rubber (C) may beused in combination with a rubber other than the olefin-based copolymerrubber (C), for example, a diene rubber such as styrene/butadiene rubber(SBR), nitrile rubber (NBR), natural rubber (NR), or butyl rubber (IIR),or a polyisobutyrene rubber of the amount that does not adversely affectthe merits of the present invention.

The elastomer (I) of the present invention is an olefin-basedthermoplastic elastomer which contains the polypropylene resin (A) andthe olefin-based copolymer rubber (C), or the polypropylene resin (A),the linear polyethylene resin (B) and the olefin-based copolymer rubber(C) at a particular content, and which has been crosslinked to a gelcontent of at least 95% by weight.

The elastomer (I) of the present invention may preferably have a meltflow rate (MFR) of 10 to 300 g/10 min, and most preferably, a melt flowrate of 20 to 200 g/10 min when evaluated in accordance with ASTM D1238under the load of 10 kg and at a temperature of 230° C.

The term “gel content” used herein is the polymer content which isinsoluble in cyclohexane, and the gel content is measured as describedbelow and calculated by the equation (1) as described below. First, asample of about 100 mg of the olefin-based thermoplastic elastomer isweighed, and the sample is cut into small pieces of 0.5 mm×0.5 mm×0.5mm. The small pieces are immersed in 30 ml of cyclohexane in a sealedcontainer at 23° C. for 48 hours.

Next, the sample is moved onto a filter paper and dried at roomtemperature for more than 72 hours until the sample weight is settled.The weight of the cyclohexane-insoluble component other than the polymercomponent (fibrous filler, filler, pigment, and the like) is subtractedfrom the weight of the dried residue to obtain “corrected final weight(Y)”. The amount of the cyclohexane-insoluble component other than thepolymer component is preliminarily calculated from the design values.

In the meanwhile, the weight of the cyclohexane-soluble component otherthan the polymer component (such as the softening agent) and the weightof the cyclohexane-insoluble component other than the polymer component(fibrous filler, filler, pigment, and the like) are subtracted from thesample weight to obtain “corrected initial weight (X)”. The amount ofthe cyclohexane-soluble component other than the polymer component ispreliminarily calculated from the design values.

The gel content (cyclohexane-insoluble component) is calculated by thefollowing equation (1):

Gel content (% by weight)=(corrected final weight (Y))÷(correctedinitial weight (X))×100  (1)

The elastomer (I) of the present invention has been crosslinked to a gelcontent of 95% or higher. For the purpose of further improvement in theoil resistance, the elastomer (I) is preferably crosslinked to a gelcontent of 97% or higher. The gel content may exceed 100% by weight, forexample, when the cyclohexane-soluble component doest not completelydissolve in the cyclohexane.

The thermoplastic elastomer (I) is produced by blending thepolypropylene resin (A) and the olefin-based copolymer rubber (C); orthe polypropylene resin (A), the linear polyethylene resin (B) and theolefin-based copolymer rubber (C) at the particular blend ratio asdescribed above, and crosslinking the mixture by a dynamic heattreatment in the presence of an organic peroxide.

Exemplary organic peroxides include dicumylperoxide,di-tert-butylperoxide, 2,5-dimethyl-2,5-di-(tert butylperoxy)hexane,2,5-dimethyl-2,5-di-(tert-butylperoxy)-hexyne-3,1,3-bis(tert-butylperoxyisopropyl)benzene,1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane,n-butyl-4,4-bis(tert-butylperoxy)valerate, benzoylperoxide,p-chlorobenzoylperoxide, 2,4-dichlorobenzoylperoxide,tert-butylperoxybenzoate, tert-butylperoxyisopropylcarbonate,diacetylperoxide, lauroylperoxide, and tert-butylcumyl-peroxide.

Among these, the preferred in view of odor and scorching stability are2,5-dimethyl-2,5-di-(tert butylperoxy)hexane,2,5-dimethyl-2,5-di-(tert-butylperoxy)-hexyne-3,1,3-bis(tert-butylperoxyisopropyl)benzene,1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, andn-butyl-4,4-bis(tert-butylperoxy)valerate. Among these, the mostpreferred are 1,3-bis(tert-butylperoxyisopropyl)benzene and2,5-dimethyl-2,5-di-(tert butylperoxy)hexane.

The organic peroxide is blended in an amount of 0.3 to 3 parts byweight, and preferably in an amount of 0.4 to 2 parts by weight per 100parts by weight of total of the polypropylene resin (A) and theolefin-based copolymer rubber (C) or 100 parts by weight of total of thepolypropylene resin (A), the linear polyethylene resin (B), and theolefin-based copolymer rubber (C). When the amount of the organicperoxide is in the range as described above, olefin-based thermoplasticelastomer (I) which has been crosslinked to a gel content of at least95% is easily obtained.

In the dynamic heat treatment as described above, sulfur; a peroxycrosslinking aid such as p-quinonedioxime, p,p′-dibenzoylquinonedioxime,N-methyl-N-4-dinitrosoaniline, nitrosobenzene, diphenylquanidine, ortrimethylolpropane-N, N′-m-phenylenedimaleimide; divinylbenzene;triallylcyanurate; a polyfunctional methacrylate monomer such asethylene glycol dimethacrylate, diethylene glycol dimethacrylate,polyethylene glycol dimethacrylate, trimethylol propane trimethacrylate,or allylmethacrylate; a polyfunctional vinyl monomer such asvinylbutylate, or vinylstearate; or the like may be added to thereaction system. These components may be added either alone or incombination of two or more. Use of such compound facilitates uniform andmild crosslinking reaction.

Of the compounds as described above, use of divinylbenzene is mostpreferable since divinylbenzene is easy to handle and highly compatiblewith the polypropylene resin (A), the linear polyethylene resin (B), andthe olefin-based copolymer rubber (C). Divinylbenzene also has thefunction of solubilizing the organic peroxide and acts as a dispersingagent of the organic peroxide. As a consequence, use of divinylbenzeneresults in uniform crosslinking in the heat treatment, and the resultingolefin-based thermoplastic elastomer (I) has well balanced flowproperties and physical properties.

The crosslinking aid or the polyfunctional vinyl monomer may be blendedpreferably in an amount of 0.2 to 3 parts by weight, and in particular,0.3 to 2 parts by weight based on 100 parts by weight of the total ofthe polypropylene resin (A) and the olefin-based copolymer rubber (C) or100 parts by weight of the total of the polypropylene resin (A), thelinear polyethylene resin (B), and the olefin-based copolymer rubber(C). When the crosslinking aid or the polyfunctional vinyl monomer isblended in the amount within the above-specified range, the crosslinkingaid or the polyfunctional vinyl monomer does not remain as unreactedmonomer in the resulting olefin-based thermoplastic elastomer (I), andthe resulting olefin-based thermoplastic elastomer (I) will not undergochange in physical properties by thermal hysteresis in the extrusion andmolding and will also exhibit high fluidity.

The dynamic heat treatment as described above is accomplished by meltkneading the components as described above in the presence of an organicperoxide, and the treatment may be carried out in a kneading system suchas mixing rolls, an intensive mixer (for example, Bambury mixer,kneader, etc.), a single-screw or twin-screw extruder, or the like, andpreferably, in a non-open type kneading system. Also, the dynamic heattreatment is preferably carried out in an inert gas such as nitrogen.

The kneading is preferably carried out at a temperature at which thehalf life of the organic peroxide used is less than 1 minute. To be morespecific, the kneading is preferably carried out at a temperature in therange of 150 to 280° C., and most preferably 170 to 240° C. The mixtureis kneaded for 1 to 20 minutes, and most preferably, for 1 to 5 minutes.The shearing force applied in kneading is typically 10 to 10⁴ sec⁻¹, andmost preferably 10² to 10⁴ sec⁻¹ at a normal shear rate.

The polyolefin resin (D) which is a critical component of the presentinvention may be an olefin polymer such as a homopolymer of an α-olefinor a copolymer of two or more α-olefins. Exemplary polyolefin resinsinclude homopolymers and copolymers of an α-olefin such as ethylene,propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene,4-methyl-1-pentene, and 3-methyl-1-pentene. Among these, the preferredare homopolymers of ethylene, propylene and 1-butene, and copolymerscontaining ethylene, propylene or 1-butene as its main component.

The polyolefin resin (D) may preferably have a melt flow rate (MFR) of0.1 to 50 g/10 min, and most preferably, a melt flow rate of 0.3 to 30g/10 min when evaluated in accordance with ASTM D1238 under the load of2.16 kg. The melt flow rate in excess of 50 g/10 min results in theinsufficient oil resistance while the melt flow rate of less than 0.1g/10 min results in the insufficient moldability.

In the present invention, content of the polyolefin resin (D) is 10 to300 parts by weight, and preferably 15 to 100 parts by weight per 100parts by weight of the elastomer (I). When the content of the polyolefinresin (D) is in such range, the resulting olefin-based thermoplasticelastomer composition will exhibit excellent resistance to oil and heatas well as good extrudability.

The olefin-based copolymer rubber (E) which is a critical component ofthe present invention may be a copolymer rubber containing an α-olefinas its main component. This copolymer rubber is an amorphous, randomelastic copolymer, and typical such copolymers include an α-olefincopolymer comprising two or more α-olefins containing 2 to 20 carbonatoms, and an α-olefin/nonconjugated diene copolymer comprising two ormore α-olefins containing 2 to 20 carbon atoms and a nonconjugateddiene.

Exemplary olefin-based copolymer rubbers include:

(1) Copolymer rubber of ethylene and an α-olefin other than ethylene

[Ethylene/(α-olefin other than ethylene (molar ratio)=90/10 to 50/50]

(2) Copolymer rubber of ethylene, an α-olefin other than ethylene, and anonconjugated diene [Ethylene/α-olefin other than ethylene (molarratio)=90/10 to 50/50]

[Ethylene/nonconjugated diene (molar ratio)=99/1 to 85/15]

(3) Copolymer rubber of propylene and an α-olefin other than propylene

[Propylene/α-olefin other than propylene (molar ratio)=90/10 to 50/50]

(4) Copolymer rubber of butene and an α-olefin other than butene

[Butene/α-olefin other than butene (molar ratio)=90/10 to 50/50]

Exemplary α-olefins include ethylene, propylene, 1-butene,4-methyl-1-pentene, 1-hexene, 1-octene, and the like. Exemplarynonconjugated dienes include dicyclopentadiene, 1,4-hexadiene,cyclooctadiene, methylene norbornene, ethylidene norbornene, and thelike.

The copolymer rubber of the above (1) to (4) may preferably have a meltflow rate of 0.1 to 5 g/10 min, and most preferably, a melt flow rate of0.2 to 2 g/10 min when evaluated in accordance with ASTM D1238 under theload of 2.16 kg and at a temperature of 190° C.

Among the copolymer rubber as described above, the olefin-basedcopolymer rubber (E) is preferably an ethylene/propylene copolymerrubber, and more preferably the one having a molar ratio of ethylene topropylene (ethylene/propylene molar ratio) in the range of 15/85 to50/50.

In the present invention, the content of the olefin-based copolymerrubber (E) is preferably in the range of 10 to 300 parts by weight, andmost preferably 10 to 100 parts by weight based on 100 parts by weightof the elastomer (I). When the content of the olefin-based copolymerrubber (E) is within such range, the resulting olefin-basedthermoplastic elastomer composition will be capable of providing anextruded article having excellent oil resistance and high flexibility.

In the present invention, the olefin-based copolymer rubber (E) may beused in combination with a rubber other than the olefin-based copolymerrubber (E), for example, a diene rubber such as styrene/butadiene rubber(SBR), nitrile rubber (NBR), natural rubber (NR), or butyl rubber (IIR),or a polyisobutyrene rubber of the amount that does not adversely affectthe merits of the present invention.

The softening agent (F) which is a critical component in the presentcomposition may be a softening agent commonly used in the production ofrubbers. Exemplary such softening agent include petroleum substancessuch as process oil, lubricating oil, paraffin, liquid paraffin,polyethylene wax, polypropylene wax, petroleum asphalt, and vaseline;coal tars such as coal tar and coal tar pitch; fatty oils such as castoroil, linseed oil, rape-seed oil, soybean oil, and palm oil; waxes suchas tall oil, beeswax, carnauba wax, and lanolin; fatty acids such aslicinoleic acid, palmitic acid, stearic acid, 12-stearic hydroxide,montanic acid, oleic acid, and erucic acid, or metal salts thereof;synthetic polymers such as petroleum resin, coumarone indene resin, andatactic polypropylene; ester plasticizers such as dioctyl phthalate,dioctyl adipate, and dioctyl sebacate; microcrystalline wax, liquidpolybutadiene or modified product or hydrogenate thereof, liquid Thiokol(trade mark), and the like.

In the present invention, content of the softening agent (F) is 10 to300 parts by weight, preferably 15 to 200 parts by weight, and morepreferably 20 to 150 parts by weight per 100 parts by weight of theelastomer (I). When the content of the softening agent (F) is in suchrange, the resulting olefin-based thermoplastic elastomer compositioncan be extruded into an article having excellent oil resistance andflexibility.

Although the composition of the present invention is the one comprisingthe elastomer (I), the polyolefin resin (D), the olefin copolymer rubber(E), and the softening agent (F), the composition may further comprisean inorganic filler (G) as described below.

The inorganic filler (G) which may be used include glass fiber,potassium titanate fiber, carbon fiber, calcium carbonate, calciumsilicate, clay, kaolin, talc, silica, diatomaceous earth, powdered mica,asbestos, alumina, barium sulfate, aluminum sulfate, calcium sulfate,magnesium carbonate, molybdenum disulfide, graphite, glass beads,shirasu balloon and the like. In the present composition, content of theinorganic filler (G) is in the range of 0 to 300 parts by weight,preferably 0 to 200 parts by weight, and most preferably 0 to 100 partsby weight per 100 parts by weight of the elastomer (I).

In addition to the components as described above, the presentcomposition may contain a thermal stabilizer, an anti-aging agent,weathering agent, an antistatic agent, a colorant, a lubricant, andother additives in the amounts that does not adversely affect the meritsof the invention.

The composition of the present invention is preferably produced byblending the elastomer (I), the polyolefin resin (D), the olefin-basedcopolymer rubber (E), and the softener (F), and optionally, theinorganic filler (G) at the particular mixing ratio as described aboveand further adding other optional additives; and subjecting the mixtureto a dynamic heat treatment under the absence of the organic peroxide.

The dynamic heat treatment as described above is accomplished by meltkneading the components as described above, and the treatment may becarried out in a kneading system such as mixing rolls, an intensivemixer (for example, Bambury mixer, kneader, etc.), a single-screw ortwin-screw extruder, and the like, and preferably, in a non-open typekneading system. Also, the dynamic heat treatment is preferably carriedout in an inert gas such as nitrogen. The components may be separatelyfed to the kneading system. Alternatively, some or all of the componentsmay be mixed before feeding to the kneading system. The inorganic filler(G) is preferably mixed with other components before feeding to thekneading system.

The kneading is carried out at a temperature higher than the meltingtemperatures of the components as described above. To be more specific,the kneading is preferably carried out at a temperature in the range of150 to 280° C., and most preferably 170 to 240° C. for a period of 0.1to 20 minutes, and most preferably, for 0.5 to 5 minutes. The shearingforce applied in kneading is typically in the range of 10 to 10⁴ sec⁻¹,and most preferably 10² to 10⁴ sec⁻¹.

The components of the present composition as described above are blendedin the amounts as described above as the general range. The components,however, are most preferably blended in the amounts within theirpreferable range. The composition wherein some components are blended inthe amounts within the preferable range and other components are blendedin the amounts within the general range are also preferable.

The components of the present composition as described above may bethose having the physical property values within the general range. Thecomponents, however, are most preferably those having the physicalproperty values within the preferable range. The components wherein somephysical property values are within the preferable range and otherphysical property values are within the general range are alsopreferable. The composition of the present invention has excellent oilresistance, and experiences reduced degree of swelling when brought incontact with non-polar solvents as aromatic organic solvents, gasolineand mineral oil.

The oil resistance of the present composition as indicated by weightdifference (ΔW, percent swell) before and after immersing in liquidparaffin at 100° C. for 24 hours is up to 150%, preferably up to 120%,and more preferably up to 100%.

The present composition has an MFR (at 230° C., under the load of 10 kg)of 0.1 to 150, preferably 0.1 to 140, and most preferably 0.1 to 120. Asa consequence, the present composition has excellent flexibility andextrudability, and the composition is highly adapted for use as a skinor surface material.

The present invention of the constitution as described above is alsoexcellent in its appearance after the extrusion in addition to theflexibility and the extrudability, and the present composition also haslightened weight and high adaptability to recycling due to the use ofthe olefin-based resin.

In addition, since the thermoplastic elastomer (I) used in theproduction of the present composition is the one which has beencrosslinked with an organic peroxide, the present composition hasimproved extrudability. As a consequence, the present composition isadequate for use as an energy-saving, resources-saving elastomer in awide variety of applications including car interior and exterior parts,industrial mechanical parts, electric and electronic parts, andconstruction materials. The present composition is particularly suitablefor use as a car interior part and skin materials.

BEST MODE FOR CARRYING OUT THE INVENTION

Next, the present invention is described in further detail by referringto Examples, which by no means limit the scope of the invention. Thecompounds used in the production of the compositions in the Examples andComparative Examples are as described below.

<Polypropylene Resin (A)>

(A-1) Propylene Homopolymer

1) MFR (ASTM D 1238-65T; 230° C.; load, 2.16 kg): 1 g/10 min

<Linear Polyethylene Resin (B)>

(B-1) Ethylene/4-methyl-1-pentene Random Copolymer

1) MFR (ASTM D 1238-65T; 230° C.; load, 2.16 kg): 2 g/10 min

2) Density: 0.940 g/cm³

(B-2) Ethylene/4-methyl-1-pentene Random Copolymer

1) MFR (ASTM D 1238-65T; 230° C.; load, 2.16 kg): 2 g/10 min

2) Density: 0.915 g/cm³

<Organic Peroxide>

2,5-dimethyl-2,5-di-(tert-butylperoxy)hexane

<Olefin-based Copolymer Rubber (C)>

(C-1) Ethylene/propylene/5-ethylidene-2-norbornene Copolymer Rubber

1) Ethylene content: 78% by mole

2) Iodine value: 14

3) Mooney viscosity (ML₁₊₄, 100° C.): 150

<Polyolefin resin (D)>

(D-1) Propylene Homopolymer

1) MFR (ASTM D 1238-65T; 230° C.; load, 2.16 kg): 0.5 g/10 min

(D-2) Ethylene/4-methyl-1-pentene Random Copolymer

1) MFR (ASTM D 1238-65T; 230° C.; load, 2.16 kg): 0.5 g/10 min

2) Density: 0.935 g/cm³

(D-3) 1-butene Homopolymer

1) MFR (ASTM D 1238-65T; 230° C.; load, 2.16 kg): 0.5 g/10 min

<Olefin-based Copolymer Rubber (E)>

(E-1) Propylene/ethylene Copolymer Rubber

1) MFR (ASTM D 1238-65T; 230° C.; load, 2.16 kg): 0.3 g/10 min

2) Ethylene content: 40% by mole

<Softening Agent (F)>

(F-1) Mineral Oil-based Process Oil (manufactured by Idemitsu KosanK.K., PW-380 (trademark)]

<Inorganic Filler (G)>

(G-1) Talc Fine Powder (manufactured by Matsumura Sangyo K.K., ET-5(trademark))

EXAMPLE 1

<Production of Thermoplastic Elastomer (I)>

25 parts by weight of pellets of propylene homopolymer (A-1), 75 partsby weight of ethylene/propylene/5-ethylidene-2-norbornene copolymerrubber (C-1), 0.4 part by weight of2,5-dimethyl-2,5-di-(tert-buthylperoxy)hexane, and 0.5 part by weight ofdivinylbenzene were thoroughly mixed, and the mixture was melt kneadedin a twin-screw extruder equipped with a screw diameter of 50 mm innitrogen atmosphere and at a temperature of 220° C. for cross linking,and the kneaded mixture was extruded to produce the pellets ofthermoplastic elastomer (I).

<Measurement of Gel Content>

Gel content was calculated by the equation (1) as described above afterextracting the pellets of thermoplastic elastomer (I) by cyclohexane.

<Production of Olefin-based Thermoplastic Elastomer Composition>

The procedure as described above were repeated except that 100 parts byweight of the resulting pellets of the elastomer (I), 50 parts by weightof the pellets of the propylene homopolymer (D-1), and 40 parts byweight of the pellets of the propylene/ethylene copolymer rubber (E-1)were thoroughly mixed, and 100 parts by weight of mineral oil-basedprocess oil (F-1) was introduced from a side feeder in the extruder asdescribed above to produce pellets of olefin-based thermoplasticelastomer composition.

<Evaluation of Physical Properties>

The resulting olefin-based thermoplastic elastomer composition wasevaluated for oil resistance and melt flow rate (MFR) by the procedureas described below, and also, for extrudability and appearance of theextrusion, and sheet extrudability by the procedure as described below.

(1) Oil Resistance

A sheet having a thickness of 2 mm was produced from the pellets of theresulting composition by using a press. A test piece of 20×20 mm(length×width) was cut out from the sheet. The test piece was immersedin liquid paraffin at 100° C. for 24 hours, and percentage weightdifference (ΔW %) before and after the immersion was measured toevaluate the oil resistance. The results are shown in Table 1.

(2) Melt Flow Rate (MFR)

The pellets were evaluated for their melt flow rate in accordance withASTM D1238 at 230° C. under the load of 10 kg. The results are shown inTable 1.

(3) Extrudability and Appearance of the Extruded Article

A single-screw extruder equipped with a screw having a diameter of 50 mmwas mounted with a die used in ASTM D 2230-90 (Garvey type), and thecomposition was extruded to obtain the extruded article.

[Extrusion Conditions]

Temperature settings: C1/C2/C3/C4/C5/H/D=160/180/200/220/220/220/200° C.

Screw revolution: 45 rpm

Screen mesh: 40/80/40 mesh

The appearance of the extruded article was evaluated by observing theskin, and the extrudability was evaluated by observing the edges. Theresults shown in the table were determined by the criteria as describedbelow.

[Criteria]

∘: good; Δ: not so good; x:poor

The results of the evaluation are shown in Table 1.

(4) Sheet Extrudability

A single-screw extruder equipped with a screw having a diameter of 65 mmwas mounted with a T die of coat hanger type, and the composition wasextruded under the conditions as described below to obtain a sheet withthe sheet thickness of 0.5 mm (lip opening of the T die: 0.7 mm).

[Extrusion Conditions]

Temperature settings:C1/C2/C3/C4/C5/C6/C7/C8/H/D=160/180/200/200/200/200/200/200/200/200° C.

Screw revolution: 50 rpm

Screen mesh: 40/80/40 mesh

The composition was extruded under the conditions as described above,and the resulting sheet was evaluated for extrusion stability such asthe stability of the sheet thickness and convenience of take up as wellas the surface conditions of the resulting sheet. The results shown inthe table were determined by the criteria as described below.

[Criteria]

∘: good; Δ: not so good; x:poor

The results of the evaluation are shown in Table 1.

EXAMPLES 2 TO 12 AND COMPARATIVE EXAMPLES 1 TO 12

Thermoplastic elastomers (I) were produced and the gel content wascalculated by repeating the procedure of Example 1 except that thecomponents and the compositional ratio of the elastomer (I) of Example 1were changed as shown in Table 1. Also, the thermoplastic elastomercompositions were produced and extruded by repeating the procedure ofExample 1 except that the components and the compositional ratio of thecomposition of Example 1 were changed as shown in Table 1 to evaluatethe physical properties of the compositions as well as the extrusionsand the extruded sheets. The results are shown in Table 1.

TABLE 1 Example 1 2 3 4 5 6 Elastomer (I) (part by weight) A-1 (PP) 2530 30 30 30 60 B-1 (LLDPE) 0 0 0 0 0 0 B-2 (LLDPE) 0 0 0 0 0 0 C-1(EPDM) 75 70 70 70 70 40 Organic peroxide 0.4 1.0 1.0 1.0 1.0 1.0Divinylbenzene 0.5 0.8 0.8 0.8 0.8 0.8 Gel content (%) 96 99 99 99 99 99Thermoplastic elastomer composition D-1 (PP) 50 50 0 0 50 20 D-2 (LLDPE)0 0 50 0 0 0 D-3 (PB) 0 0 0 50 0 0 E-1 (PER) 40 20 20 20 20 20 E-1 (Oil)100 50 50 50 50 20 G-1 (Talc) 0 0 0 0 10 0 Oil resistance (wt. %) 128 8998 97 88 72 MFR (g/10 min) 130 180 190 190 150 80 Extruded articleExtrudability Skin ◯ ◯ ◯ ◯ ◯ ◯ Edge ◯◯ ◯ ◯ ◯ ◯ Sheet extrudabilityStability ◯ X X X Δ ◯ Surface ◯ ◯ ◯ ◯ ◯ ◯ conditions Example 7 8 9 10 1112 Elastomer (I) (part by weight) A-1 (PP) 20 25 25 25 25 60 B-1 (LLDPE)5 10 10 10 10 10 B-2 (LLDPE) 0 0 0 0 0 0 C-1 (EPDM) 75 65 65 65 65 30Organic peroxide 0.4 1.0 1.0 1.0 1.0 1.0 Divinylbenzene 0.5 0.8 0.8 0.80.8 0.8 Gel content (%) 97 99 99 99 99 99 Thermoplastic elastomercomposition D-1 (PP) 40 50 0 0 50 20 D-2 (LLDPE) 0 0 50 0 0 0 D-3 (PB) 00 0 50 0 0 E-1 (PER) 50 20 20 20 20 20 F-1 (Oil) 100 50 50 50 50 20 G-1(Talc) 0 0 0 0 10 0 Oil resistance (wt. %) 124 64 71 69 62 53 MFR (g/10min) 90 120 150 150 100 40 Extruded article Extrudability Skin ◯ ◯ ◯ ◯ ◯◯ Edge ◯ ◯ ◯ ◯ ◯ ◯ Sheet extrudability Stability ◯ ◯ Δ Δ ◯ ◯ Surfaceconditions ◯ ◯ ◯ ◯ ◯ ◯ Comparative Example 1 2 3 4 5 6 Elastomer (I)(part by weight) A-1 (PP) 30 30 30 30 30 60 B-1 (LLDPE) 0 0 0 0 0 0 B-2(LLDPE) 0 0 0 0 0 0 C-1 (EPDM) 70 70 70 70 70 70 Organic peroxide 0.151.0 1.0 1.0 1.0 1.0 Divinylbenzene 0.15 0.8 0.8 0.8 0.8 0.8 Gel content(%) 91 99 99 99 99 99 Thermoplastic elastomer composition D-1 (PP) 50 5050 0 50 0 D-2 (LLDPE) 0 0 0 0 0 0 D-3 (PB) 0 0 0 0 0 0 E-1 (PER) 20 20 020 0 0 F-1 (Oil) 50 0 50 50 0 0 G-1 (Talc) 0 0 0 0 0 0 Oil resistance(wt. %) 178 118 78 129 95 128 MFR (g/10 min) 150 90 170 120 50 30Extruded article Extrudability Skin ◯ ◯ ◯ ◯ ◯ X Edge ◯ Δ Δ Δ Δ X Sheetextrudability Stability Δ ◯ X ◯ ◯ ◯ Surface conditions ◯ Δ Δ Δ Δ XComparative Example 7 8 9 10 11 12 Elastomer (I) (part by weight) A-1(PP) 25 25 25 25 25 60 B-1 (LLDPE) 10 0 10 10 10 10 B-2 (LLDPE) 0 10 0 00 0 C-1 (EPDM) 65 65 65 65 65 30 Organic peroxide 0.15 1.0 1.0 1.0 1.01.0 Divinylbenzene 0.15 0.8 0.8 0.8 0.8 0.8 Gel content (%) 93 99 99 9999 99 Thermoplastic elastomer composition D-1 (PP) 50 50 0 50 50 0 D-2(LLDPE) 0 0 0 0 0 0 D-3 (PB) 0 0 0 0 0 0 E-1 (PER) 20 20 20 0 20 0 F-1(Oil) 50 50 50 50 0 0 G-1 (Talc) 0 0 0 0 0 0 Oil resistance (wt. %) 173195 78 51 98 43 MFR (g/10 min) 80 120 90 150 30 20 Extruded articleExtrudability Skin ◯ ◯ ◯ ◯ ◯ X Edge ◯ Δ Δ Δ Δ X Sheet extrudabilityStability ◯ ◯ Δ Δ ◯ ◯ Surface conditions ◯ ◯ Δ Δ Δ X The unit of thecontent of each component is part by weight.

A-1: propylene homopolymer (PP), MFR 1

B-1: ethylene/4-methyl-1-pentene random copolymer (LLDPE), density 0.940

B-2: ethylene/4-methyl-1-pentene random copolymer (LLDPE), density 0.915

C-1: ethylene/propylene/5-ethylidene-2-norbornene copolymer rubber(EPDM)

Organic peroxide: 2,5-dimethyl-2,5-di-(tert-butylperoxy) hexane

D-1: propylene homopolymer (PP), MFR 0.5

D-2: ethylene/4-methyl-1-pentene random copolymer (LLDPE), density 0.935

D-3: 1-butene homopolymer (PB)

E-1: propylene-ethylene copolymer rubber (PER)

F-1: mineral oil based process oil

G-1: talc fine powder

Industrial Utility

The olefin-based thermoplastic elastomer composition of the presentinvention contains a thermoplastic elastomer comprising polypropyleneresin, an olefin-based copolymer rubber, and a linear polyethylene resinas an optional component, and which is crosslinked to a gel content ofat least 95%, and therefore, the composition of the present inventionhas excellent oil resistance. In addition to the thermoplasticelastomer, the composition of the present invention contains apolyolefin resin, an olefin-based copolymer rubber, and a softeningagent, and therefore, the composition enjoys excellent flexibility,extrudability and good appearance of the extruded article.

What is claimed is:
 1. A thermoplastic elastomer composition having aweight difference (ΔW) before and after immersing in liquid paraffin at100° C. for 24 hours of up to 150%, said composition comprising (I) 100parts by weight of an elastomer which has been produced bv subjecting acomposition containing components (A) and (C) described below to dynamicheat treatment in the presence of an organic peroxide and which has beencrosslinked to a gel content of at least 95%: (A) 20 to 90 parts byweight of a polypropylene resin having a melt flow rate of 0.1 to 5 g/10min when the melt flow rate is measured under a load of 2.16 kg and atemperature of 230° C. in accordance with ASTM D1238, and (C) 10 to 80parts by weight of an olefin copolymer rubber, wherein (A)+(C)=100 partsby weight; (D) 10 to 300 parts by weight of a polyolefin resin; (E) 10to 300 parts by weight of an olefin copolymer rubber; and (F) 10 to 300parts by weight of a softening agent.
 2. A thermoplastic elastomercomposition having a weight difference (ΔW) before and after immersingin liquid paraffin at 100° C. for 24 hours of up to 150%, saidcomposition comprising (I) 100 parts by weight of an elastomer which hasbeen produced by subjecting a composition containing components (A),(B), and (C) described below to dynamic heat treatment in the presenceof an organic peroxide and which has been crosslinked to a gel contentof at least 95%: (A) 20 to 90 parts by weight of a polypropylene resinhaving a melt flow rate of 0.1 to 5 g/10 min when the melt flow rate ismeasured under a load of 2.16 kg and a temperature of 230° C. inaccordance with ASTM D1238, (B) 5 to 30 parts by weight of a linearpolyethylene resin having a density of 0.920 to 0.950 g/cm³, and (C) 5to 75 parts by weight of an olefin copolymer rubber, wherein(A)+(B)+(C)=100 parts by weight; (D) 10 to 300 parts by weight of apolyolefin resin; (E) 10 to 300 parts by weight of an olefin copolymerrubber; and (F) 10 to 300 parts by weight of a softening agent.